Slide preheating means for projectors



Jan. 7, 1964 H. E. ROSENBERGER ETAL 3,

SLIDE PREHEATING MEANS FOR PROJECTORS 2 Sheets-Sheet 1 Original Filed Dec. 26, 1956 INVENTORS HARO LD E. ROSENBERG ER BY RICHARD F SCHUMA ATTORNEYS mulllllnm. 7

H. E. ROSENBERGER ETAL 3,116,662

SLIDE PREHEATING MEANS FOR PROJECTORS Original Filed Dec. 26, 1956 Jan. 7, 1964 2 Sheets-Sheet 2' INVENTORS HAROLD E. ROSEN BERGER y RIC RD SCHUMA ATTORNEYS United States Patent 3,116,662 SLIDE PREHEATING MEANS FGR PRQJECTURS Harold 1E. Rosenberger, Brighton, N.Y., and Richard F. Schuma, Santa Barbara, Qalih, assignors to Bausch dz Lamb incorporated, Rochester, N.Y., a corporation of New York Continuation of application Ser. No. 65%,479, Dec. 26, 1956. This application Feb. 23, 1%2, Ser. No. 176,487

3 Claims. (Cl. 8828) This invention relates to projection apparatus and more particularly it has reference to projectors of the type which are used to project images of transparencies such as films and slides.

This is a continuation of our copending application erial No. 630,479, filed December 26, 1956, now abandoned.

Films which are supported only at their edges during projection, are subject to buckling under the action of heat which reaches the film from the projection light source. Therefore, when projecting an image on a screen, the operator would initially focus the projector for a slide as the same is brought into projecting position, and after buckling or popping has occurred he would have to refocus the projector in order to have the projected image sharply in focus. -In the widely used colored film transparencies or slides, the emulsion coated film is held in aperturcd cardboard mounts so that the picture area is unsupported and when such slides are projected they are subject to buckling due to heat in the projected light beam so that refocusing of the projector is necessitated.

One of the objects of this invention is to provide a projector which will overcome the aforementioned disadvantages.

Another object of the present invention is to provide a projector in which slides are pro-conditioned in order to buckle them before they are stationed in projection position.

The present invention takes the form of an improvement for slide projectors and comprises an electrically operated fan which is adapted to draw cool surrounding air into the projector for cooling the same. An air duct is arranged in the projector and has its inlet located in such a relationship with the housing for the light source for receiving a portion of the hot air in the vicinity of the light source. The outlet of the air duct is so situated as to direct the tlow of hot air onto a plurality of slides which are located in a slide magazine tray adjacent the position from which a manual or automatic sliding mechanism will engage a slide to move the same into viewing position. In this manner, hot air, of a temperature sufiicient to buckle the film, is applied to a number of slides before they are moved into alignment with the optical system of the projector thereby inducing buckling of the film in the slides and conditioning the film for the particular projecting arrangement of the optical system.

A second or auxiliary air duct is also arranged in the projector and has its inlet located between the high pressure or downstream side of the fan and the light source for directing cool air to a slide which is in projecting position adjacent the condenser lens. This duct serves to direct the flow of cool air to the slide in order to prevent the excessive heat, generated by the light source and transmitted through the condenser lens, from damaging the film in the slide. As will appear hereinafter, the novel aspect of this invention resides in the arrangement of the air flow means relative to the fan and the light source and the hot air duct for the pre-condition-ing of the slides.

Other objects and advantages will appear from the fol- 3,llh,hh2 Patented Jan. 7, 1964 lowing description taken in conjunction with the drawings wherein:

FIG. 1 is a plan View, partly in section, showing the present invention incorporated in a slide projector;

FIG. 2 is a sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary sectional view through part of the magazine tray and optical system as viewed along the line 33 of FIG. 1 and the line 3-3 of FIG. 2; and

FIG. 4 is a fragmentary sectional view as viewed along the line 4-4 of MG. 1.

A conventional slide projector is shown generally at 10 in FIG. 1 and comprises a base or casing 12, a lamp housing 14, an optical system or lens assembly gene-rally indicated at .16 and a slide magazine tray generally indicated at 18.

As shown in FIGS. 2 and 4, the base 12 consists of upper and lower dish-shaped castings 2d and 2 2, respectively, and these are fastened together along their rims by bolts 24. Mounted interiorly and adjacent one end of the base is an electric motor 26 which serves to rotate a shaft 28 extending vertically downwardly from the motor. A radial flow impeller 30 is mounted and secured to the remote end of the shaft 28. A vertically disposed bathe plate 32 having its ends secured to an end wall 34 of the upper casting 20 and curved around the motor 26 cooperates with the undersurface of the casting 2d and a horizontally projecting plate 36 to form a manifold 38 for the fan 30. The manifold serves to converge the air flow entering the base 12 from a slit 4'3 formed in the wall 34, as shown by the arrows.

Projecting laterally from one wall of the upper casting and integrally therewith and extending inwardly of the base is a plate 42 for supporting a light source or bulb 44. Suitable bolts to are used to fasten the bulb socket ii: to the plate 42, as shown in FIG. 4. A bulb shield or housing Sit in the form of a box of various parts, is secured to the upper casting 20 by any suitable means and is in communication with the chamber formed in the base 12 through an outlet 49 of the chamber. To the rear of the shie d St) is attached a reflector 52 while at the forward end of the shield there is a wall 54 having grooves 56 for receiving and retaining the edges of condensing lens The top of the shield is covered with a plate 60 having a plurality of apertures 62 for permitting the escape of some of the heat developed in the housing 50 by the light source. To complete the structure of the shield a pair of parallel spaced apart side walls 64, 66 are fastened to and between the reflector 52 and the front wall 54, with the side wall 64 positioned between the bulb 44- and the tray 18.

The condensing lens 58 constitutes part of the optical system 16 and cooperating with the lens 58 is an objective lens 68 adjustably mounted on the upper casting 2h in any suitable manner but in such a position as to be in the path of the projected light beam. Intermediate the condensing lens 58 and the adjacent element '76 of the objective lens 68 and coaxially aligned therewith is a slide frame holder '72 which may be rigidly mounted on the casting 20. The holder '72 comprises a pair of upper and lower rails 74, 76 which are formed with inwardly opposed grooves 78, 89, respectively, for slidingly holding a film slide 82 which, when in the position shown in FIG. 3, is in the path of the projected light beam.

The film slide 82 is normally carried in the magazine tray 18 which may house anywhere up to 48 slides and for purposes of the invention any suitable sliding mechanism of the automatic or manually actuated type may be employed to remove a slide from the tray 18, position it in the frame holder 72 and return the slide to its previous position within the tray. For purposes of simplicity, a manually actuated sliding mechanism is shown and takes bet vcen the lenses 53 and the form of a slide 84 slidably mounted on a horizontally dispos l 86 which is mounted on tl e base 12 by a pair of uprights secured th reto. A curved finger 33 is secured to one end of the head 24 and serves to remove the slide 82 from the tray 13 and a second finger 92 secured to the other end of the head serves to return the slide to the tray when the head is moved to toe left right, respectively.

In the position, shown in FIG. 3, the finger 9% has completed its movement to the right and has carried along therewith the slide In this position of the slide, both the finger 96 and a stop arm 94 secured to and proiecting "from one of the uprights U serve to maintain the slide 82 in a relatively rigid and centered projection position Movement of the head 84- to the left will disengage the slide from the finger 9t) and bring the finger in er nt with the edge of the l dge slide Whcrenpon further leftward movement of the head for purposes of description, a type employing a gear rack is shown. The gear rack 38 may be formed on the frame of the tray or be a separate rack mounted in the tray and is utilized for feeding the tray in one direction for positioning each of the various film slides 32 successively in alignment with the slide frame 72. A gear 1%, secured to one end of a shaft M92 which is rotatably mounted in an upstanding portion Ell-d of the base 12, serves to move the tray 16 upon step by step rotation of the shaft 102. A knob 1% on the other end of the shaft remote from the gea lit-ll is provided to facilitate manual rotation of the gear. It will be apparent that an operator may position a film slide to be projected in alignment with the frame '72 by simply manipulating the knob H96 until this is accomplished. By actuating the head 8 to its position shown in FIG. 3 a slide 82 will be removed from the tray and positioned in the frame 72.

The magazine tray is is adapted to be inserted in a tunnel or tray container 1% which comprises a top plate ill) and side plates 112-, 114 secured together and with the upper casting to form an elongated box-like frame open at both ends to permit the movement or" the tray 18 therethrough. The tray is adapted to be supported on and guided by a pair of elongated shoulders 115 formed on the casting 29 immediately below the holder 1'98.

As seen in FIGS. 1 and 2, the side wall 64 of the housor bulb snield is formed with a generally rectangular opening it in immediate adjacency to the bulb A curved plate 113 is connected at one end to the wall 64 along one edge 12d of the opening 116 and at the other end to the wall 122 of the container lit-*3. All angled wall .122 is connected at one end to the wall 64 along the other edge 124- of opening 116 remote from t.e edge 12@ and at the other end to the wall 112. Both the plate 118 and the wall 322 extend vertically between and are connected to an extension 325 of the top plate 115* and a similarly sh ped plate projecting from the lower end of the wall The wall ll is formed with a relatively narrow rectangular cut out or vent 139 along its forward edge and as sh wn in FIG. 2, this cut out opening is or" slightly smaller area than the opening 116.

It will be apparent that the plate 118, the walls 112, 122, the top wall extension 126 and the bottom plate 12-8 define an enclosed chamber 132 which serves as an air duct for the passage of air therethrough. The chamber 132 is in communication with the space defined by the housing 59 so as to receive some of the heat developed by the bulb 44. Similarly, the opening 13% connects the 4 chamber 52 with the space within the container 108.

As shown in FIG. 1, the opening 139 is aligned with at least two slides 32a, 82b which are immediately behind the normal position 320 of the slide 82 in the tray 18. In this manner, each of the slides 82a, 82b will be opposite the opening 130 for twopositionings of the tray during the course of successive projection of the slides 82. When the slide 82 is moved back to its position on the tray and the latter is advanced a distance of one slide spacing, the slide 82b will be in position to be moved into projecting position and the slide 82a will be in the position formerly occupied by the slide 82b. The slide immediately behind the slide will occupy the position previously occupied by the slide 82a after the latter is advanced.

Another air duct is provided in the projector and to this end, the upper casting 2.6 of the base 12 is provided with an opening 13d located between the lenses 58 and 7G and adjacent the lower rail 76. Bafile plates 136 are fastened upon the upper and lower surfaces of the casting in order to extend the depth of the opening 134 and control the tlow of air therethrough. As shown by the arrows in FlGS. 2 and 3, air flows from the interior of the base 22, through the opening 134- and is directed along the adjacent surface of the slide 82 for a purpose which will appear hereinafter.

Operation It will be assumed that the electric current supply (not shown) for the projector 19 is such as to be able to energize the electric motor 26 and the bulb 44 simultaneously, or, at least, will permit operation of the motor before the bulb is allowed to become energized. Since circuits of this sort are well known in the art, further description of the same will be unnecessary.

With the motor 26 energized and the fan rotating, relatively cool air will be drawn from the surrounding atmosphere through the slot 46 and into the base 12 which will serve as an air duct for the transmission of As previously indicated, the bafiles 36 will permit the tunneling or" air into the fan intake in order to increase the efiici ncy of the fan. The flow of air is then directed upwardly through the outlet 49 and into the lamp housing where the air is permitted to circulate around the bulb 4-4 to be heated thereby. Some of the air is then allowed to escape through the openings 62 formed in the top cover 60 of the shield in order to permit cooling of the bulb 44. It will be apparent that in the movement of air just described, the air flow is rather rapid in view of the work imposed upon the air by the fan thus permitting efi'lcient cooling of the bulb 44.

Some of the hot air flowing through the housing is conducted past the opening 116 and through the duct or chamber 132, being forced therefrom through the opening 13%. The hot air flowing through the opening 339 impinges upon both surfaces of the two film slides 82a, 62]) causing buckling of the same as they stand in readiness to be moved into projecting position. It will be noted that the relative areas of the openings 116 and I136 are such as to cause a relatively faster rate of flow of the hot air through the opening for heating the slides. The areas of these parts, the fan capacity and the openings 62 are accordingly dimensioned in order to allow only enough heat to come in communication with the film slides for causing buckling without any danger of damaging the film in the slides.

Some of the cool air under pressure in the base 12 flows through the opening 134 and impinges upon the slide $2, which is in projecting position, in order to cool the same against the heat that is developed in the vicinity of the slide by the light source and transmitted through the condensing lens The opening 134 is of an area to allow only enough air to pass thercthrough for cooling the slide to prevent the overheating of the slide and damage thereof.

As the slide is returned to slot 820 in the tray 13 it still is in a heated and popped condition. The returned slide operates as a heat barrier in the slide tray tending to minimize the loss of heat due to radiation and convection currents which facilitates film buckling or popping by uniformly heating, and maintaining an even temperature of the films next to be moved into projection position.

From the foregoing description, it will be appreciated that the present invention provides means for directing the flow of hot air upon a plurality of film slides just prior to their movement into projecting position thereby inducing buckling or popping of the film. This preconditioning of the film slides and maintaining of the popped condition of the slide obviates the need for refocusing the slide when in projecting position and results in a continuous accurately-focused projection of all the slides which are to be projected. It will also be appreciated that the work upon the air is performed by a fan located between the intake of the projector base and the bulb thereby eliminating the heating of the fan and motor by the bulb. The length of the duct between the lamp housing and the slides to-be-preconditioned is held to a minimum, consequently more heat is available to utilize in the pre-conditioning step while at the same time allowing most of the heat to escape from the shield for efficient cooling of the bulb.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form is shown for purpose of illustration, and that the same may be modified and embodied in various other forms or employed in other uses without departing from its spirit or the scope of the appended claims.

We claim:

1. A projection apparatus comprising in combination, a light source, a housing defining a chamber means receiving said light source, a slide holder holding a slide in the projecting position, a lens system aligned with said light source and said slide holder, a slide tray, a tray retainer receiving said tray, a slide transfer mechanism associated with said tray for transferring slides from said tray to said slide holder and for returning slides from said holder to said tray, air moving means, passage means com municating with said air moving means and said chamber means directing the flow of cooling air through said chamber means, first communicating means connecting said chamber means and said tray retainer providing flow of heated air from said chamber means around a plurality of slides to preheat and prepop the slides prior to positioning in said slide holder, a second communicating means connected to said air moving means directing air over the slide in said slide holder and maintaining the desired slide temperature of the slide disposed in said holder.

2. A projection apparatus comprising in combination, a light source, a housing defining a chamber means receiving said light source, a slide holder holding a slide in a projecting position, a lens system aligned with said light source and said slide holder, a tray retainer mounted adjacent said slide holder, a slide tray received in said tray retainer, slide transfer mechanism associated with said tray for transferring a slide from said tray to said slide holder, air moving means, passage means com municating with said air moving means and said chamber means conveying cooling air through said chamber means, a first communicating means connecting said chamber means with said tray retainer conveying heated air for heating and pre-popping of slides prior to transfer to said slide holder, a second communicating means connected to said air moving means conveying air to said slide holder thereby preventing overheating of the slide in said slide holder and maintaining a uniformly heated and popped condition on the slide in the projecting position, said slide transfer mechanism returning the heated slide to said tray subsequent to projection of the image, the returned heated slide thereby providing a heat barrier in said tray for minimizing heat loss and stabilizing the temperature of the slides in said tray prior to transfer to said slide holder.

3. A projection apparatus comprising in combination, a light source, a housing defining a chamber means receiving said light source, a slide holder associated with said light source, a lens system aligned with said light source and said slide holder, air pressurizing means mounted in the projection apparatus, passage means communicating with said pressurizing means and said chamber means providing conveyance of cooling air through said chamber means, a tray retainer adjacent said slide holder, a slide tray received in said tray retainer, transfer means associated with said tray for transferring a slide from said tray to said holder and returning the slide from said holder to said tray, a first communicating means connecting said cham ber means and said tray retainer to provide passage of heated air from said chamber means for pre-popping of slides immediately prior to transfer of the slide in the tray to said holder, a second communicating means connected to said air pressurizing means directing air on the slide in said slide holder maintaining a pre-popped condition of the slide therein and preventing overheating of said slide during projection of the image from the slide in said holder, said transfer means returning said slide from said holder to said tray thereby providing a heat barrier to minimize heat loss in said tray due to convection currents and radiation within said tray for maintaining a uniform temperature of the slides in said tray adjacent said slide holder.

References Cited in the file of this patent UNITED STATES PATENTS 2,038,784 Ghadiali Apr. 28, 1936 2,294,219 Woermann Aug. 25, 1942 2,362,601 Wengel Nov. 14, 1944 2,590,492 Bennet et al Mar. 25, 1952 2,627,017 Howard Jan. 27, 1953 3,000,258 Misuraca Sept. 19, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noe 3,,ll6 662 January 'Z, 19264 l -larold Ea Rosenberger et a1, It is hereby certif ied that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 19 before "tray insert the column 6 line 15 for "on" read of =0 Signed and sealed this 9th day of June 1964?,

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A PROJECTION APPARATUS COMPRISING IN COMBINATION, A LIGHT SOURCE, A HOUSING DEFINING A CHAMBER MEANS RECEIVING SAID LIGHT SOURCE, A SLIDE HOLDER HOLDING A SLIDE IN THE PROJECTING POSITION, A LENS SYSTEM ALIGNED WITH SAID LIGHT SOURCE AND SAID HOLDER, A SLIDE TRAY, A TRAY RETAINER RECEIVING SAID TRAY, A SLIDE TRANSFER MECHANISM ASSOCIATED WITH SAID TRAY TRANSFERRING SLIDES FROM SAID TRAY TO SAID SLIDE HOLDER AND FOR RETURNING SLIDES FROM SAID HOLDER TO SAID TRAY, AIR MOVING MEANS, PASSAGE MEANS COMMUNICATING WITH SAID AIR MOVING MEANS AND SAID CHAMBER MEANS DIRECTING THE FLOW OF COOLING AIR THROUGH SAID CHAMBER MEANS, FIRST COMMUNICATING MEANS CONNECTING SAID CHAMBER MEANS AND SAID TRAY RETAINER PROVIDING FLOW OF HEATED AIR FROM SAID CHAMBER MEANS AROUND A PLURALITY OF SLIDES TO PREHEAT AND PREPOP THE SLIDES PRIOR TO POSITIONING IN SAID SLIDE HOLDER, A SECOND COMMUNICATING MEANS CONNECTED TO SAID AIR MOVING MEANS DIRECTING AIR OVER THE SLIDE HOLDER AND MAINTAINING THE DESIRED SLIDE TEMPERATURE OF THE SLIDE DISPOSED IN SAID HOLDER. 